Luby's Tortilla Soup

Source: Houston Chronicle

3 quarts chicken stock
1 1/2 (12 ounce) cans whole peeled tomatoes
2 3/4 teaspoons ground cumin
1/2 clove garlic, minced
1 tablespoon salt
2 1/2 teaspoons ground pepper
1 1/2 (12 ounce) cans cream style corn
3 1/2 cups shredded American cheese
1/2 cup cornstarch
1 cup cool water
1 pound ground beef
1/3 cup chopped onion
Tortilla chips

Bring broth to a boil in a large pot. Crush tomatoes by hand and add with juice to broth. Add cumin, garlic, salt, pepper, corn, and cheese. Bring to a boil again.

Dissolve cornstarch in cup of cool water in small bowl. Add to boiling soup slowly while stirring constantly. Let simmer 10 minutes.

While soup simmers, saut